Although cochlear implants are highly successful in both children and adults, there is a wide range of performance across patients. More knowledge is needed to understand the nature of these critical differences. Furthermore, knowledge about these differences must be translated into practical solutions so that all patients can obtain maximum benefit from their cochlear implants. The present studies are aimed at understanding the factors that contribute to individual performance and at improving performance through modifications to the signal processors. We believe that we are in a unique position to identify underlying factors contributing to individual differences and to apply this knowledge to benefit the patient because of the experience and expertise of our group, the facilities available to us, and the large and committed patient population. Three adult studies are proposed. The aim of the first study will be to improve individual performance by evaluating the effects of systematic modifications to the continuous interleaved sampling speech processing strategy. These improvements will be achieved by using electrophysiological measures, by studying the consequences of varying a wide range of parameters, and by developing clinically practical adaptive strategies. In a second study, we will implant both ears of 10 patients. Extensive preoperative measures will be obtained, allowing evaluation of possible correlations between pre- and postoperative measures using a within-subjects control. The results may provide guidance on which ear to implant in the usual application when only one ear is implanted. This experiment will also allow the investigation of binaural cochlear implants. Experiments are planned for adjusting and evaluating independent and interactive binaural processors. In the third adult study, we will develop statistical models to predict postimplant speech perception from predictor variables in this and the other projects. Long term evaluation of our patients who already have implants is included. Two studies are planned with prelingually deafened children. One will develop statistical models to predict postimplant success based on preimplant measures. The second study involves adjustments to individual processors based on physiological measurements.